Spontaneous Piezoelectric Effect As Order Parameter In (Nh4)(2)Cubr4 Center Dot 2h(2)O Crystal

Temperature change of piezoelectric properties of (NH4)(2)CuBr4 center dot 2H(2)O crystal in the low -temperature ferroelastoelectric phase is studied. The macroscopic order parameter is proved to be the h(36) component of the spontaneous piezoelectric tensor. The critical exponent related with the phase transition is alpha=0.60 +/- 0.05. (C) 2016 Elsevier B.V. All rights reserved.